Problem with landlords as tenant references

[Mark Hu]

I;ve noticed that many landlords, especially large companies, are reluctant to give out tenant information, even with faxed signed applications. Often I only get time of rental and whether they paid rent on time.
Usually I assume when they limit info like that that the tenant is not good.
It has me spooked so that now I am reluctant to give out anything unless the tenant was very good. What is the reason for this? Is it the threat of lawsuits, or some laws? This is Southern California.

Thanks